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Python 3.8.0b2

Release Date: July 4, 2019

This is a beta preview of Python 3.8

Python 3.8 is still in development. This release, 3.8.0b2 is the second of four planned beta release previews. Beta release previews are intended to give the wider community the opportunity to test new features and bug fixes and to prepare their projects to support the new feature release.

Call to action

We strongly encourage maintainers of third-party Python projects to test with 3.8 during the beta phase and report issues found to the Python bug tracker as soon as possible. While the release is planned to be feature complete entering the beta phase, it is possible that features may be modified or, in rare cases, deleted up until the start of the release candidate phase (2019-09-30). Our goal is have no ABI changes after beta 3 and no code changes after 3.8.0rc1, the release candidate. To achieve that, it will be extremely important to get as much exposure for 3.8 as possible during the beta phase.

Please keep in mind that this is a preview release and its use is not recommended for production environments.

Major new features of the 3.8 series, compared to 3.7

Some of the new major new features and changes in Python 3.8 are:

  • PEP 572, Assignment expressions
  • PEP 570, Positional-only arguments
  • PEP 587, Python Initialization Configuration (improved embedding)
  • PEP 590, Vectorcall: a fast calling protocol for CPython
  • PEP 578, Runtime audit hooks
  • PEP 574, Pickle protocol 5 with out-of-band data
  • Typing-related: PEP 591 (Final qualifier), PEP 586 (Literal types), and PEP 589 (TypedDict)
  • Parallel filesystem cache for compiled bytecode
  • Debug builds share ABI as release builds
  • f-strings support a handy = specifier for debugging
  • continue is now legal in finally: blocks
  • on Windows, the default asyncio event loop is now ProactorEventLoop
  • on macOS, the spawn start method is now used by default in multiprocessing
  • multiprocessing can now use shared memory segments to avoid pickling costs between processes
  • typed_ast is merged back to CPython
  • LOAD_GLOBAL is now 40% faster
  • pickle now uses Protocol 4 by default, improving performance
  • (Hey, fellow core developer, if a feature you find important is missing from this list, let Ɓukasz know.)

There are many other interesting changes, please consult the "What's New" page in the documentation for a full list.

The next pre-release of Python 3.8 will be 3.8.0b3, currently scheduled for 2019-07-29.

More resources

And now for something completely different

Jones: Morning, Squadron Leader.
Idle: What-ho, Squiffy.
Jones: How was it?
Idle: Top-hole. Bally Jerry, pranged his kite right in the how's-your-father; hairy blighter, dicky-birded, feathered back on his sammy, took a waspy, flipped over on his Betty Harpers and caught his can in the Bertie.
Jones: Er, I'm afraid I don't quite follow you, Squadron Leader.
Idle: It's perfectly ordinary banter, Squiffy. Bally Jerry, pranged his kite right in the how's-your-father; hairy blighter, dicky-birded, feathered back on his sammy, took a waspy, flipped over on his Betty Harpers and caught his can in the Bertie.
Jones: No, I'm just not understanding banter at all well today. Give us it slower.
Idle: Banter's not the same if you say it slower, Squiffy.

Full Changelog


Version Operating System Description MD5 Sum File Size GPG
Gzipped source tarball Source release 5921bc797ecb65fb73a6c6f760408cc4 23735411 SIG
XZ compressed source tarball Source release 45f82dd4e05b4cb40406123dc7bf5f14 17638912 SIG
macOS 64-bit installer macOS for OS X 10.9 and later 5d7b48ad646bf8c130edb4a6bbc9b860 28754925 SIG
Windows help file Windows f079d8065a2f0d3bfe04035e9ebc8401 8360025 SIG
Windows x86-64 embeddable zip file Windows for AMD64/EM64T/x64 059c6931d4dc663045e9f64b2fce7eeb 7935697 SIG
Windows x86-64 executable installer Windows for AMD64/EM64T/x64 7feb4bfac2eba20c755b3f552fc86267 27178336 SIG
Windows x86-64 web-based installer Windows for AMD64/EM64T/x64 019f677d012d960c1d3900e48b8c3c4f 1363240 SIG
Windows x86 embeddable zip file Windows fcf4c144227ebeadbf12e0c3d6cc729d 7190767 SIG
Windows x86 executable installer Windows aaeb2342ed79fa2966d9ef1ffc3178a7 26175800 SIG
Windows x86 web-based installer Windows aa3627a949b28f03afa2c0df9ff5f9dd 1324768 SIG